Dryer felts



I. W. JONES Aug. 14, 1962 DRYER FELTS Filed Oct. 12, 1959 United StatesPatent Ofiice 3,049,153 Patented Aug. 14, 1962 3,049,153 DRYER FELTSlidris W. .iones, Lachute, Quebec, Canada, assignor to Ayers Limited,Lacnnte Mills, Quebec, Canada Filed Get. 12, 1959, Ser. No. 845,876Claims priority, application Canada Sept. 15, 1959 3 Claims. (til.139-426) This invention relates to improvements in dryer felts for pulpand paper machines.

A particular object of this invention is to provide an improved feltcomposed of at least a substantial percentage of a polyethyleneterephthalic yarn, which is known in the trade as Terylene in which theweft yarns are pretreated to stabilize the woven fabric against lateralshrinkage.

A further object is to provide a felt of the character described inwhich the warp yarns are formed of a composite synthetic and naturalyarns which permit of controlled stretch and shrinkage in the warpwisedirection of the woven fabric.

Heretofore, dryer felts of Terylene composition have had considerablesuccess as to strength and wear resistance. However, the maindisadvantage in the use of T erylene is that it is subject toprogressive shrinkage under certain conditions of temperature andhumidity. On the paper machine there is nothing to restrain or exert astretching pull in the weftwise or cross direction so that normalTerylene reinforced weft yarns are subjected to progressive shrinkage,and this is further induced by the normal stretch or pull in the wrap orlengthwise direction of the felt.

The primary tendency to shrink of the reinforced Weft yarns can beoffset by heat relaxing the filament yarns at definite elevatedtemperatures before being incorporated with the asbestos roving mix intothe final weft yarn.

Ordinary warp yarns of natural fibres (asbestos-cotton) tend to stretchexcessively when subjected to the tensions set up operating around thedryers and rolls of the paper machine under hot humid conditions. Theaddition of a controlled amount of untreated Terylene filament yarnplied with the natural fibre warp yarns tends to cause shrinkage andoffset this stretching and provide a stabilized fabric keeping the feltsufficiently tight to perform its drying and driving functions.

The present invention proposes to overcome the disadvantages outlinedabove by the introduction of a pretreated, substantially Terylene weftyarn which reduces lateral shrinkage of the woven fabric to a minimumand by the introduction of a composite Terylene and other fibrous Warpyarn which is designed to control the stretch and shrinkage of the feltin the warp-wise direction of the felt.

Proceeding now to a more detailed description, reference will be had tothe accompanying drawings, in which:

FIG. 1 is a view showing the weave of a 3-ply felt of "Ierylene andcomposite yarns embodying this invention.

FIG. 2 is a side view of a weft yarn shown in FIG. 1.

FIG. 3 is an end view of the yarn shown in FIG. 2.

FIG. 4 is a side view of one form of 'a warp yarn shown in FIG. 1.

FIG. 5 is an end view of the yarn shown in FIG. 4.

FIG. 6 is a side view of another form of a warp yarn shown in FIG. 1.

Referring more particularly to FIG. 1, the dryer felt is shown to be3-ply construction but may be of Q. or more plies, including weft yarns5 interwoven with warp yarns 6 and 7. In the particular embodiment thewarp yarns 6 interwoven with the weft yarns forms a facing ply, the Warpyarns 7 interwoven with the weft yarns 5 forms a backing ply and acombination of warp yarns 6 and 7 interwoven with the weft yarns 5 formsa filling ply.

As shown, particularly in FIGS. 2 and 3 each weft yarn 5 comprises afilament Terylene core 10 which may consist of one or more strands ofTerylene filaments twisted together. The filament or filaments ofTerylene are pre-treated by being stress relaxed at a temperature offrom about 300 F. to about 400 F. to cause a pro-shrinkage. Thepre-treated core 10 is then surrounded by an asbestos-cotton orasbestos-Terylene staple fibre blend 11 which is spirally wound aboutthe Terylene core 10 to provide a protective covering for the same.

In the warp certain of these yarns are illustrated in FIG. 4 and othersare illustrated in FIG. 5. In FIG. 4 the warp yarn 6 preferably consistsof a core of non-treated Terylene filament twisted with a cotton strand16. The core is then surrounded by a protective covering 17 of mixedasbestos-cotton or mixed asbestos-Terylene fibres. This combination coreand covering controls shrinkage in the warpwise direction of the dryerfelt. The warp yarn 6 forms a durable face ply which resists wear on thesurface of the felt. This composite warp yarn 6 also reduces thetendency of progressive stretch.

The backing ply warp yarns 7 are formed by twisting one or more strandsof non-heat set T erylene filaments 18 with cotton yarn. This warp yarn7 also has a controlled stretch in the warpwise direction of the dryerfelt.

Where the dryer felt calls for a '3-ply construction the warps of theintermediate or filling ply may be alternately of the construction ofWarp yarns 6 and 7 or may be arranged substantially as shown in FIG. 1.

While the foregoing is believed to be illustrative of a preferredembodiment of this invention, it is to be understood that changes andmodifications may be resorted to within the scope and spirit of thisinvention as defined in the appended claims.

What I claim is:

1. An improved woven dryer felt for use in the manufacture of pulp andpaper products comprising weft yarns including a core of shrinkresistant polyethlene terephthalic filaments with a protective coveringof staple fibers wound thereover and warp yarns including a core ofpolyethylene terephthalic shrinkable filaments and a protective coveringof staple fibers whereby shrinkage is minimized in the weftwisedirection and shrinkage and expansion in the Warpwise direction ispermitted.

2. An improved dryer felt according to claim 1 wherein the warp yarncore includes cotton strands twisted with the shrinkable polyethyleneterephthalic filaments.

3. An improved dryer felt according to claim 1 wherein the protectivecovering of both the weft and warp yarn comprises asbestos fibers mixedwith cotton fibers.

References Cited in the file of this patent UNITED STATES PATENTS2,450,948 Foster Oct. 12, 1948 2,821,771 Skeer Feb. 4, 1958 2,865,409Asten Dec. 23, 1958 FOREIGN PATENTS 702,046 Great Britain Jan. 6, 1954708,936 Great Britain May 12, 1954

